Liquid containers have various types of closures. Some closures have tubes, such as straws, for withdrawing liquid from the container. When liquid is withdrawn from the container, through the tube, a negative pressure may be created within the container, thus making it more difficult to further withdraw liquid. To address this problem, various types of vents have been used to allow air into the container and equalize the pressure between the inside of the container and the outside atmosphere.
In addition to equalizing the relative pressure within a container, it may also be desirable to prevent liquid from escaping the container through the vent, if the container is tilted or knocked over. It would be beneficial to provide a vented closure for a container that allowed pressure equalizing air to enter the container and restricted unwanted outward flow of liquid from the container.